This invention relates to controls for turbine type power plants and more particularly to means for synthesizing a failed sensor to avoid engine shutdown or damage.
The apparent consequence of a sensor which is no longer operating within its operating envelope in an engine control is failure or shutdown of the engine. Obviously, such a consequence is to be avoided if at all possible. Attempts have been made to account for failed sensors particularly as a result of the advent of digital computers. For example, U.S. Pat. No. 3,851,157 granted to S. H. Ellis on Nov. 26, 1974, and assigned to the same assignee, discloses a system that continuously performs mathematical calculations and applies a statistical analysis of sorts to ascertain the probability of sensor failure and means that would substitute for the failed sensor. Such a system is not only complex but is cumbersome to implement and at best it's a statistical approach to the correct answer.
I have found that I can increase failure tolerance of electronic controls by synthesizing many of the sensed engine parameters upon their failure. This invention contemplates generating a function that is indicative of the ratio of two engine parameters where one of those parameters include the term of the failed parameter. This ratio is then multiplied by a given engine parameter which has a given thermodynamic relationship in that particular engine cycle and the product is a synthesized value indicative of the failed sensor.